Power Generation using Independent Dual Organic Rankine Cycles from Waste Heat Systems in Diesel Hydrotreating-Hydrocracking and Continuous-Catalytic-Cracking-Aromatics Facilities

ABSTRACT

Optimizing power generation from waste heat in large industrial facilities such as petroleum refineries by utilizing a subset of all available hot source streams selected based, in part, on considerations for example, capital cost, ease of operation, economics of scale power generation, a number of organic Rankine cycle (ORC) machines to be operated, operating conditions of each ORC machine, combinations of them, or other considerations are described. Subsets of hot sources that are optimized to provide waste heat to one or more ORC machines for power generation are also described. Further, recognizing that the utilization of waste heat from all available hot sources in a mega-site such as a petroleum refinery and aromatics complex is not necessarily or not always the best option, hot source units in petroleum refineries from which waste heat can be consolidated to power the one or more ORC machines are identified.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority under 35 U.S.C. §119 to U.S.Provisional Patent Application Ser. No. 62/209,217, filed on Aug. 24,2015; U.S. Provisional Patent Application Ser. No. 62/209,147, filed onAug. 24, 2015; U.S. Provisional Patent Application Ser. No. 62/209,188,filed on Aug. 24, 2015; and U.S. Provisional Patent Application Ser. No.62/209,223, filed on Aug. 24, 2015. The entire contents of each of thepreceding applications are incorporated herein by reference in theirrespective entireties.

TECHNICAL FIELD

This specification relates to power generation in industrial facilities.

BACKGROUND

Petroleum refining processes are chemical engineering processes andother facilities used in petroleum refineries to transform crude oilinto products, for example, liquefied petroleum gas (LPG), gasoline,kerosene, jet fuel, diesel oils, fuel oils, and other products.Petroleum refineries are large industrial complexes that involve manydifferent processing units and auxiliary facilities, for example,utility units, storage tanks, and other auxiliary facilities. Eachrefinery can have its own unique arrangement and combination of refiningprocesses determined, for example, by the refinery location, desiredproducts, economic considerations, or other factors. The petroleumrefining processes that are implemented to transform the crude oil intothe products such as those listed earlier can generate heat, which maynot be re-used, and byproducts, for example, greenhouse gases (GHG),which may pollute the atmosphere. It is believed that the world'senvironment has been negatively affected by global warming caused, inpart, due to the release of GHG into the atmosphere.

SUMMARY

This specification describes technologies relating to power generationfrom waste energy in industrial facilities. The present disclosureincludes one or more of the following units of measure with theircorresponding abbreviations, as shown in Table 1:

TABLE 1 Unit of Measure Abbreviation Degrees Celsius ° C. Megawatts MWOne million MM British thermal unit Btu Hour h Pounds per square inch(pressure) psi Kilogram (mass) Kg Second S

The details of one or more implementations of the subject matterdescribed in this specification are set forth in the accompanyingdrawings and the description later. Other features, aspects, andadvantages of the subject matter will become apparent from thedescription, the drawings, and the claims.

BRIEF DESCRIPTION OF DRAWINGS

FIGS. 1A-1T are schematic illustrations of a power generation systemthat utilizes waste heat from one or more heat sources in apetrochemical refining plant.

FIGS. 1U-1X are graphs that illustrate heat exchanger performance ofheat exchangers in the power generation system shown in FIGS. 1S-1T.

DETAILED DESCRIPTION

Industrial waste heat is a source for potential carbon-free powergeneration in many industrial facilities, for example, crude oilrefineries, petrochemical and chemical complexes, and other industrialfacilities. For example, a medium-size integrated crude oil refinerywith aromatics up to 4,000 MM Btu/h can be wasted to a network of aircoolers extended along the crude oil and aromatics site. Some of thewasted heat can be used to power an Organic Rankine Cycle (ORC) machine,which uses an organic fluid such as refrigerants or hydrocarbons (orboth) instead of water to generate power. ORC machines in combinationwith low temperature heat sources (for example, about 232° C. or less)are being implemented as power generation systems. Optimizing ORCmachines, for example, by optimizing the power generation cycle (thatis, the Rankine cycle) or the organic fluid implemented by the ORCmachine (or both), can improve power generation from recovered wasteheat.

An industrial facility such as a petroleum refinery includes severalsources of waste heat. One or more ORC machines can receive the wasteheat from one or more or all of such sources. In some implementations,two or more sources of low grade heat can be consolidated bytransferring heat from each of the sources to a common intermediate heattransfer medium (for example, water or other fluid). The intermediateheat transfer medium can then be used to evaporate the working fluid ofthe ORC machine to generate power, for example, to operate a turbine orother power generator. Such consolidation of sources of low grade heatcan allow the ORC machine to be sized to realize greater efficienciesand economies of scale. Further, such a consolidated operation canimprove flexibility in petroleum refinery design and plot spaceplanning, since each heat source need not be in close proximity to thepower generator. The proposed consolidation of heat sources,particularly, in mega sites such as a site-wide oil refinery thatincludes an aromatics complex and is the size of an eco-industrial parkcan represent an over-simplification of the problem of improving theprocess of recovering waste heat to generate power.

This disclosure describes optimizing power generation from waste heat,for example, low grade heat at a temperature at or less than 160° C. inlarge industrial facilities (for example, petroleum refineries or otherlarge industrial refineries with several, sometimes more than 50, hotsource streams) by utilizing a subset of all available hot sourcestreams selected based, in part, on considerations for example, capitalcost, ease of operation, economics of scale power generation, a numberof ORC machines to be operated, operating conditions of each ORCmachine, combinations of them, or other considerations. Recognizing thatseveral subsets of hot sources can be identified from among theavailable hot sources in a large petroleum refinery, this disclosuredescribes selecting subsets of hot sources that are optimized to providewaste heat to one or more ORC machines for power generation. Further,recognizing that the utilization of waste heat from all available hotsources in a mega-site such as a petroleum refinery and aromaticscomplex is not necessarily or not always the best option, thisdisclosure identifies hot source units in petroleum refineries fromwhich waste heat can be consolidated to power the one or more ORCmachines.

This disclosure also describes modifying medium grade crude oil refiningsemi-conversion facilities and integrated medium grade crude oilrefining semi-conversion and aromatics facilities plants' designs toimprove their energy efficiencies relative to their current designs. Todo so, new facilities can be designed or existing facilities can bere-designed (for example, retro-fitted with equipment) to recover wasteheat, for example, low grade waste heat, from heat sources to power ORCmachines. In particular, the existing design of a plant need not besignificantly altered to accommodate the power generation techniquesdescribed here. The generated power can be used, in part, to power thefacilities or transported to the electricity grid to be deliveredelsewhere (or both).

By recovering all or part of the waste heat generated by one or moreprocesses or facilities (or both) of industrial facilities andconverting the recovered waste heat into power, carbon-free power (forexample, in the form of electricity) can be generated for use by thecommunity. The minimum approach temperature used in the waste heatrecovery processes can be as low as 3° C. and the generated power can beas high as 80 MW. In some implementations, higher minimum approachtemperatures can be used in an initial phase at the expense of lesswaste heat/energy recovery, while relatively better power generation(for example, in terms of economy of scale design and efficiency) isrealized in a subsequent phase upon using the minimum approachtemperature for the specific hot sources uses. In such situations, morepower generation can be realized in the subsequent phase without needingto change the design topology of the initial phase or the subset of thelow grade waste hot sources used in the initial phase (or both).

Not only pollution associated but also cost associated with powergeneration can be decreased. In addition, recovering waste heat from acustomized group of hot sources to power one or more ORC machines ismore optimal than recovering waste heat from all available hot sources.Selecting the hot sources in the customized group instead of or inaddition to optimizing the ORC machine can improve or optimize (or both)the process of generating power from recovered waste heat. If a fewnumber of hot sources are used for power generation, then the hotsources can be consolidated into few (for example, one or two) bufferstreams using fluids, for example, hot oil or high pressure hot watersystem, or a mixture of the two.

In sum, this disclosure describes several petroleum refinery-wideseparation/distillation networks, configurations, and processing schemesfor efficient power generation using a basic ORC machine operating underspecified conditions. The power generation is facilitated by obtainingall or part of waste heat, for example, low grade waste heat, carried bymultiple, scattered low grade energy quality process streams. In someimplementations, the ORC machine uses separate organic material topre-heat the exchanger and evaporator and uses other organic fluid, forexample, iso-butane, at specific operating conditions.

Examples of Petroleum Refinery Plants

Industrial waste heat is a source for potential carbon-free powergeneration in many industrial facilities, for example, crude oilrefineries, petrochemical and chemical complexes, and other industrialfacilities. For example, a medium-size integrated crude oil refinerywith aromatics up to 4,000 MM Btu/h can be wasted to a network of aircoolers extended along the crude oil and aromatics site. Some of thewasted heat can be used to power an Organic Rankine Cycle (ORC) machine,which uses an organic fluid such as refrigerants or hydrocarbons (orboth) instead of water to generate power. ORC machines in combinationwith low temperature heat sources (for example, about or less than 232°C.) are being implemented as power generation systems. Optimizing ORCmachines, for example, by optimizing the power generation cycle (thatis, the Rankine cycle) or the organic fluid implemented by the ORCmachine (or both), can improve power generation from recovered wasteheat.

An industrial facility such as a petroleum refinery includes severalsources of waste heat. One or more ORC machines can receive the wasteheat from one or more or all of such sources. In some implementations,two or more sources of low grade heat can be consolidated bytransferring heat from each of the sources to a common intermediate heattransfer medium (for example, water or other fluid). The intermediateheat transfer medium can then be used to evaporate the working fluid ofthe ORC machine to generate power, for example, to operate a turbine orother power generator. Such consolidation of sources of low grade heatcan allow the ORC machine to be sized to realize greater efficienciesand economies of scale. Further, such a consolidated operation canimprove flexibility in petroleum refinery design and plot spaceplanning, since each heat source need not be in close proximity to thepower generator. The proposed consolidation of heat sources,particularly, in mega sites such as a site-wide oil refinery thatincludes an aromatics complex and is the size of an eco-industrial parkcan represent an over-simplification of the problem of improving theprocess of recovering waste heat to generate power.

This disclosure describes optimizing power generation from waste heat,for example, low grade heat at a temperature at or less than 160° C. inlarge industrial facilities (for example, petroleum refineries or otherlarge industrial refineries with several, sometimes more than 50, hotsource streams) by utilizing a subset of all available hot sourcestreams selected based, in part, on considerations for example, capitalcost, ease of operation, economics of scale power generation, a numberof ORC machines to be operated, operating conditions of each ORCmachine, combinations of them, or other considerations. Recognizing thatseveral subsets of hot sources can be identified from among theavailable hot sources in a large petroleum refinery, this disclosuredescribes selecting subsets of hot sources that are optimized to providewaste heat to one or more ORC machines for power generation. Further,recognizing that the utilization of waste heat from all available hotsources in a mega-site such as a petroleum refinery and aromaticscomplex is not necessarily or not always the best option, thisdisclosure identifies hot source units in petroleum refineries fromwhich waste heat can be consolidated to power the one or more ORCmachines.

This disclosure also describes modifying medium grade crude oil refiningsemi-conversion facilities and integrated medium grade crude oilrefining semi-conversion and aromatics facilities plants' designs toimprove their energy efficiencies relative to their current designs. Todo so, new facilities can be designed or existing facilities can bere-designed (for example, retro-fitted with equipment) to recover wasteheat, for example, low grade waste heat, from heat sources to power ORCmachines. In particular, the existing design of a plant need not besignificantly altered to accommodate the power generation techniquesdescribed here. The generated power can be used, in part, to power thefacilities or transported to the electricity grid to be deliveredelsewhere (or both).

By recovering all or part of the waste heat generated by one or moreprocesses or facilities of industrial facilities (or both) andconverting the recovered waste heat into power, carbon-free power (forexample, in the form of electricity) can be generated for use by thecommunity. The minimum approach temperature used in the waste heatrecovery processes can be as low as 3° C. and the generated power can beas high as 80 MW. In some implementations, higher minimum approachtemperatures can be used in an initial phase at the expense of lesswaste heat/energy recovery, while relatively better power generation(for example, in terms of economy of scale design and efficiency) isrealized in a subsequent phase upon using the minimum approachtemperature for the specific hot sources uses. In such situations, morepower generation can be realized in the subsequent phase without needingto change the design topology of the initial phase or the subset of thelow grade waste hot sources used in the initial phase (or both).

Not only pollution associated but also cost associated with powergeneration can be decreased. In addition, recovering waste heat from acustomized group of hot sources to power one or more ORC machines ismore cost effective from a capital cost point-of-view than recoveringwaste heat from all available hot sources. Selecting the hot sources inthe customized group instead of or in addition to optimizing the ORCmachine can improve or optimize the process of generating power fromrecovered waste heat (or both). If a few number of hot sources are usedfor power generation, then the hot sources can be consolidated into few(for example, one or two) buffer streams using fluids, for example, hotoil or high pressure hot water system (or both).

In sum, this disclosure describes several petroleum refinery-wideseparation/distillation networks, configurations, and processing schemesfor efficient power generation using a basic ORC machine operating underspecified conditions. The power generation is facilitated by obtainingall or part of waste heat, for example, low grade waste heat, carried bymultiple, scattered low grade energy quality process streams. In someimplementations, the ORC machine uses separate organic material topre-heat the exchanger and evaporator and uses other organic fluid, forexample, isobutane, at specific operating conditions.

Examples of Petroleum Refinery Plants

1. Hydrocracking Plant

Hydrocracking is a two-stage process combining catalytic cracking andhydrogenation. In this process heavy feedstocks are cracked in thepresence of hydrogen to produce more desirable products. The processemploys high pressure, high temperature, a catalyst, and hydrogen.Hydrocracking is used for feedstocks that are difficult to process byeither catalytic cracking or reforming, since these feedstocks arecharacterized usually by high polycyclic aromatic content or highconcentrations of the two principal catalyst poisons, sulfur andnitrogen compounds (or both).

The hydrocracking process depends on the nature of the feedstock and therelative rates of the two competing reactions, hydrogenation andcracking. Heavy aromatic feedstock is converted into lighter productsunder a wide range of high pressures and high temperatures in thepresence of hydrogen and special catalysts. When the feedstock has ahigh paraffinic content, hydrogen prevents the formation of polycyclicaromatic compounds. Hydrogen also reduces tar formation and preventsbuildup of coke on the catalyst. Hydrogenation additionally convertssulfur and nitrogen compounds present in the feedstock to hydrogensulfide and ammonia. Hydrocracking produces isobutane for alkylationfeedstock, and also performs isomerization for pour-point control andsmoke-point control, both of which are important in high-quality jetfuel.

2. Diesel Hydrotreating Plant

Hydrotreating is a refinery process for reducing sulfur, nitrogen andaromatics while enhancing cetane number, density and smoke point.Hydrotreating assists the refining industry's efforts to meet the globaltrend for stringent clean fuels specifications, the growing demand fortransportation fuels and the shift toward diesel. In this process, freshfeed is heated and mixed with hydrogen. Reactor effluent exchanges heatwith the combined feed and heats recycle gas and stripper charge.Sulphide (for example, ammonium bisulphide and hydrogen sulphide) isthen removed from the feed.

3. Aromatics Complex

A typical aromatics complex includes a combination of process units forthe production of basic petrochemical intermediates of benzene, tolueneand xylenes (BTX) using the catalytic reforming of naphtha usingcontinuous catalyst regeneration (CCR) technology.

4. Naphtha Hydrotreating Plant and Continuous Catalytic Reformer Plants

A Naphtha Hydrotreater (NHT) produces 101 Research Octane Number (RON)reformate, with a maximum 4.0 psi Reid Vapor Pressure (RVP), as ablending stock in the gasoline pool. It usually has the flexibility toprocess blends of Naphtha from the Crude Unit, Gas Condensate Splitter,Hydrocracker, Light Straight-Run Naphtha (LSRN) and Visbreaker Plants.The NHT processes naphtha to produce desulfurized feed for thecontinuous catalyst regeneration (CCR) platformer and gasoline blending.

5. Crude Distillation Plant

Normally, a two-stage distillation plant processes various crude oilsthat are fractionated into different products, which are furtherprocessed in downstream facilities to produce liquefied petroleum gas(LPG), Naphtha, Motor Gasoline, Kerosene, Jet Fuel, Diesel, Fuel Oil andAsphalt. The Crude Distillation plant can typically process largevolumes, for example, hundreds of thousands of barrels, of crude oil perday. During the summer months the optimum processing capacity maydecrease. The plant can process mixture of crudes. The plant can alsohave asphalt producing facilities. The products from crude distillationplant are LPG, stabilized whole naphtha, kerosene, diesel, heavy diesel,and vacuum residuum. The Atmospheric Column receives the crude chargeand separates it into overhead product, kerosene, diesel, and reducedcrude. The Naphtha stabilizer may receive the atmospheric overheadstream and separates it into LPG and stabilized naphtha. The reducedcrude is charged to the Vacuum tower where it is further separated intoheavy diesel, vacuum gas oils and vacuum residuum.

6. Sour Water Stripping Utility Plant (SWSUP)

The SWSUP receives sour water streams from acid gas removal, sulfurrecovery, and flare units, and the sour gas stripped and released fromthe soot water flash vessel. The SWSUP strips the sour components,primarily carbon dioxide (CO2), hydrogen sulfide (H₂S) and ammonia(NH₃), from the sour water stream.

One of more of the refinery plants described earlier can supply heat,for example, in the form of low grade waste heat, to the ORC machinewith reasonable economics of scale, for example, tens of megawatts ofpower. Studies have shown that particular refinery plants, for example,a hydrocracking plant, serve as good waste heat sources to generatepower. However, in a study using only the hot source from the naphthahydrotreating (NHT) plant, for example, at about 111° C., 1.7 MW ofpower was produced from about 27.6 MW of available waste heat at a lowefficiency of about 6.2%. The low efficiency suggests that a hot sourcefrom the NHT plant alone is not recommended for waste heat generationdue to high capital and economy of scale. In another study using one lowgrade hot source at about 97° C. from a crude distillation plant, 3.5 MWof power was produced from about 64.4 MW of available waste heat at alow efficiency of 5.3%. In a further study using one low grade hotsource at about 120° C. from a sour water stripping plant, 2.2 MW ofpower was produced from about 32.7 MW of available waste heat at a lowefficiency of 6.7%. These studies reveal that if waste heat recoveryfrom a particular refinery plant to generate power is determined to bebeneficial, it does not necessarily follow that waste heat recovery fromany refinery plant will also be beneficial.

In another study, all waste heat available from all hot sources(totaling 11 hot source streams) in an aromatics complex were collectedto generate about 13 MW of power from about 241 MW of available wasteheat. This study reveals that using all available hot sources, whiletheoretically efficient, does not, in practice, necessarily translate toefficient power generation from available waste heat. Moreover,assembling power plants that can use all available hot sources can bevery difficult considering the quantity of heat exchangers, pumps, andorganic-based turbines (among other components and inter-connectors)involved. Not only will it be difficult to retrofit existing refineriesto accommodate such power plants, but it will also be difficult to buildsuch power plants from a grass roots stage. In the following sections,this disclosure describes combinations of hot sources selected fromdifferent refinery plants which can result in high efficiencies ingenerating power from available waste heat.

Even after identifying specific hot sources to be used for powergeneration in a mega-size site, there can be several combinations of hotsources that can be integrated for optimum generation of power using aspecific ORC machine operating under specific conditions. Each of thefollowing sections describes a specific combination of hot sources and aconfiguration for buffer systems which can be implemented with thespecific combination to optimally generate power from waste heat with asminimum capital utilization as necessary. Also, the following sectionsdescribe two-buffer systems for low grade waste heat recovery whereone-buffer systems for waste heat recovery as inapplicable. Each sectiondescribes the interconnections and related processing schemes betweenthe different plants that make up the specific combination of hotsources, the configurations including components such as heat exchangersadded in specific plants, at specific places and to specific streams inthe process to optimize waste heat recovery and power generation. Asdescribed later, the different configurations can be implemented withoutchanging the current layout or processes implemented by the differentplants. The new configurations described in the sections later cangenerate between about 34 MW and about 80 MW of power from waste heat,enabling a proportional decrease of GHG emissions in petroleumrefineries. The configurations described in the sections laterdemonstrate more than one way to achieve desired energy recovery usingbuffer systems. The configurations are related processing schemes do notimpact and can be integrated with future potential in-plant energysaving initiatives, for example, low pressure steam generation. Theconfigurations and processing schemes can render more than 10% first lawefficiency for power generation from the low grade waste heat into theORC machine.

Heat Exchangers

In the configurations described in this disclosure, heat exchangers areused to transfer heat from one medium (for example, a stream flowingthrough a plant in a crude oil refining facility, a buffer fluid orother medium) to another medium (for example, a buffer fluid ordifferent stream flowing through a plant in the crude oil facility).Heat exchangers are devices which transfer (exchange) heat typicallyfrom a hotter fluid stream to a relatively less hotter fluid stream.Heat exchangers can be used in heating and cooling applications, forexample, in refrigerators, air conditions or other cooling applications.Heat exchangers can be distinguished from one another based on thedirection in which liquids flow. For example, heat exchangers can beparallel-flow, cross-flow or counter-current. In parallel-flow heatexchangers, both fluid involved move in the same direction, entering andexiting the heat exchanger side-by-side. In cross-flow heat exchangers,the fluid path runs perpendicular to one another. In counter-currentheat exchangers, the fluid paths flow in opposite directions, with onefluid exiting whether the other fluid enters. Counter-current heatexchangers are sometimes more effective than the other types of heatexchangers.

In addition to classifying heat exchangers based on fluid direction,heat exchangers can also be classified based on their construction. Someheat exchangers are constructed of multiple tubes. Some heat exchangersinclude plates with room for fluid to flow in between. Some heatexchangers enable heat exchange from liquid to liquid, while some heatexchangers enable heat exchange using other media.

Heat exchangers in crude oil refining and petrochemical facilities areoften shell and tube type heat exchangers which include multiple tubesthrough which liquid flows. The tubes are divided into two sets—thefirst set contains the liquid to be heated or cooled; the second setcontains the liquid responsible for triggering the heat exchange, inother words, the fluid that either removes heat from the first set oftubes by absorbing and transmitting the heat away or warms the first setby transmitting its own heat to the liquid inside. When designing thistype of exchanger, care must be taken in determining the correct tubewall thickness as well as tube diameter, to allow optimum heat exchange.In terms of flow, shell and tube heat exchangers can assume any of threeflow path patterns.

Heat exchangers in crude oil refining and petrochemical facilities canalso be plate and frame type heat exchangers. Plate heat exchangersinclude thin plates joined together with a small amount of space inbetween, often maintained by a rubber gasket. The surface area is large,and the corners of each rectangular plate feature an opening throughwhich fluid can flow between plates, extracting heat from the plates asit flows. The fluid channels themselves alternate hot and cold liquids,meaning that the heat exchangers can effectively cool as well as heatfluid. Because plate heat exchangers have large surface area, they cansometimes be more effective than shell and tube heat exchangers.

Other types of heat exchangers can include regenerative heat exchangersand adiabatic wheel heat exchangers. In a regenerative heat exchanger,the same fluid is passed along both sides of the exchanger, which can beeither a plate heat exchanger or a shell and tube heat exchanger.Because the fluid can get very hot, the exiting fluid is used to warmthe incoming fluid, maintaining a near constant temperature. Energy issaved in a regenerative heat exchanger because the process is cyclical,with almost all relative heat being transferred from the exiting fluidto the incoming fluid. To maintain a constant temperature, a smallquantity of extra energy is needed to raise and lower the overall fluidtemperature. In the adiabatic wheel heat exchanger, an intermediateliquid is used to store heat, which is then transferred to the oppositeside of the heat exchanger. An adiabatic wheel consists of a large wheelwith threats that rotate through the liquids—both hot and cold—toextract or transfer heat. The heat exchangers described in thisdisclosure can include any one of the heat exchangers described earlier,other heat exchangers, or combinations of them.

Each heat exchanger in each configuration can be associated with arespective thermal duty (or heat duty). The thermal duty of a heatexchanger can be defined as an amount of heat that can be transferred bythe heat exchanger from the hot stream to the cold stream. The amount ofheat can be calculated from the conditions and thermal properties ofboth the hot and cold streams. From the hot stream point of view, thethermal duty of the heat exchanger is the product of the hot stream flowrate, the hot stream specific heat, and a difference in temperaturebetween the hot stream inlet temperature to the heat exchanger and thehot stream outlet temperature from the heat exchanger. From the coldstream point of view, the thermal duty of the heat exchanger is theproduct of the cold stream flow rate, the cold stream specific heat anda difference in temperature between the cold stream outlet from the heatexchanger and the cold stream inlet temperature from the heat exchanger.In several applications, the two quantities can be considered equalassuming no heat loss to the environment for these units, particularly,where the units are well insulated. The thermal duty of a heat exchangercan be measured in watts (W), megawatts (MW), millions of BritishThermal Units per hour (Btu/hr), or millions of kilocalories per hour(Kcal/h). In the configurations described here, the thermal duties ofthe heat exchangers are provided as being “about X MW,” where “X”represents a numerical thermal duty value. The numerical thermal dutyvalue is not absolute. That is, the actual thermal duty of a heatexchanger can be approximately equal to X, greater than X or less thanX.

Flow Control System

In each of the configurations described later, process streams (alsocalled “streams”) are flowed within each plant in a crude oil refiningfacility and between plants in the crude oil refining facility. Theprocess streams can be flowed using one or more flow control systemsimplemented throughout the crude oil refining facility. A flow controlsystem can include one or more flow pumps to pump the process streams,one or more flow pipes through which the process streams are flowed andone or more valves to regulate the flow of streams through the pipes.

In some implementations, a flow control system can be operated manually.For example, an operator can set a flow rate for each pump and set valveopen or close positions to regulate the flow of the process streamsthrough the pipes in the flow control system. Once the operator has setthe flow rates and the valve open or close positions for all flowcontrol systems distributed across the crude oil refining facility, theflow control system can flow the streams within a plant or betweenplants under constant flow conditions, for example, constant volumetricrate or other flow conditions. To change the flow conditions, theoperator can manually operate the flow control system, for example, bychanging the pump flow rate or the valve open or close position.

In some implementations, a flow control system can be operatedautomatically. For example, the flow control system can be connected toa computer system to operate the flow control system. The computersystem can include a computer-readable medium storing instructions (suchas flow control instructions and other instructions) executable by oneor more processors to perform operations (such as flow controloperations). An operator can set the flow rates and the valve open orclose positions for all flow control systems distributed across thecrude oil refining facility using the computer system. In suchimplementations, the operator can manually change the flow conditions byproviding inputs through the computer system. Also, in suchimplementations, the computer system can automatically (that is, withoutmanual intervention) control one or more of the flow control systems,for example, using feedback systems implemented in one or more plantsand connected to the computer system. For example, a sensor (such as apressure sensor, temperature sensor or other sensor) can be connected toa pipe through which a process stream flows. The sensor can monitor andprovide a flow condition (such as a pressure, temperature, or other flowcondition) of the process stream to the computer system. In response tothe flow condition exceeding a threshold (such as a threshold pressurevalue, a threshold temperature value, or other threshold value), thecomputer system can automatically perform operations. For example, ifthe pressure or temperature in the pipe exceeds the threshold pressurevalue or the threshold temperature value, respectively, the computersystem can provide a signal to the pump to decrease a flow rate, asignal to open a valve to relieve the pressure, a signal to shut downprocess stream flow, or other signals.

FIGS. 1A-1U illustrate schematic views of an example system 100 for apower conversion network that includes waste heat sources associatedwith a diesel hydrotreating-hydrocracking plant and acontinuous-catalytic-cracking-aromatics plant. In this example system100, a mini-power plant synthesis uses two independent circuits of ORCsystems, sharing hot water (or other heating fluid) and isobutanesystems infrastructure, to generate power from specific portions of acrude oil refining-petrochemical site-wide low-low grade waste heatsources, including hydrocracking, diesel hydrotreating and CCR,aromatics plants. In some aspects, the system 100 can be implemented inone or more steps, where each phase can be separately implementedwithout hindering future steps to implement the system 100. In someaspects, a minimum approach temperature across a heat exchanger used totransfer heat from a heat source to a working fluid (for example, water)can be as low as 3° C. or may be higher. Higher minimum approachtemperatures can be used in the beginning of the phases at the expenseof less waste heat recovery and power generation, while reasonable powergeneration economics of scale designs are still attractive in the levelof tens of megawatts of power generation.

In some aspects of system 100, optimized efficiency is realized uponusing a minimum approach temperature recommended for the specific heatsource streams used in the system design. In such example situations,optimized power generation can be realized without re-changing theinitial topology or the sub-set of low grade waste heat streamsselected/utilized from the whole crude oil refining-petrochemicalcomplex utilized in an initial phase. System 100 and its related processscheme can be implemented for safety and operability through two ORCsystems using one or more buffer streams such as hot oil or highpressure hot water systems or a mix of specified connections amongbuffer systems. The low-low grade waste-heat-to-power-conversion (forexample, lower than the low grade waste heat temperature defined by U.S.Department of Energy DOE as 232° C.) may be implemented using one ormore ORC systems using isobutane as an organic fluid at specificoperating conditions using two buffer systems shared by the two systemsof power generation but can be working independently too. In someaspects of system 100, one of the two ORC systems has only an evaporatorwhile the other ORC system has an evaporator and pre-heater.

System 100 may not change with future changes inside individualhydrocracking, hydrotreating, CCR, and aromatics plants to enhanceenergy efficiency and system 100 may not need to be changed uponimprovements in plant waste heat recovery practices, such as heatintegration among hot and cold streams. System 100 may use “low-low”grade waste heat, below 160° C. available in heat sources in the mediumlevel crude oil semi-conversion refining facilities and aromaticscomplex.

FIGS. 1A-1B is a schematic diagram of an example system 100 for a powerconversion network that includes waste heat sources associated with adiesel hydrotreating-hydrocracking plant and acontinuous-catalytic-cracking-aromatics plant. In this exampleimplementation, system 100 utilizes twenty-three distinct heat sourcesthat feed heat through a working fluid (for example, hot water, hot oil,or otherwise) to two ORC systems to produce power. In the illustratedexample, the twenty-three heat sources are separated among three heatrecovery circuits. For instance, heat recovery circuit 102 includes heatexchangers 102 a-102 j. Heat recovery circuit 103 includes heatexchangers 103 a-103 c. Heat recovery circuit 105 includes heatexchangers 105 a-105 j.

In the illustrated example, each heat exchanger facilitates heatrecovery from a heat source in a particular industrial unit to theworking fluid. For example, heat exchangers 102 a-102 c recover heatfrom heat sources in a para-xylene separation unit. Heat exchangers 102d-102 e recover heat from heat sources in a para-xylene isomerizationreaction and separation unit(s). Heat exchanger 102 f recovers heat froma heat source(s) in a benzene extraction unit. Heat exchangers 102 g-102j recover heat from heat sources in a continuous catalytic reformingplant (CCR). Together, heat exchangers in the heat recovery circuit 102recover low grade waste heat from specific streams in a “Naphtha Block”to deliver the heat via the working fluid to an ORC 104 a. In thisexample, the heat from heat recovery circuit 102 is provided to apre-heater 106 a of the ORC 104 a.

Generally, the heat recovery circuit 102 receives (for example, from aninlet header that fluidly couples a heating fluid tank 116 to the heatexchangers 102 a-102 j) high pressure working fluid (for example, hotwater, hot oil, or otherwise) for instance, at between about 40° C. to60° C. and supplies heated fluid (for example, at an outlet headerfluidly coupled to the heat exchangers 102 a-102 j) at or about 100-115°C. The heat exchangers 102 a-102 j may be positioned or distributedalong the CCR-Aromatics module complex and fluidly coupled to low gradewaste heat sources from the refining-petrochemical plants. Para-Xyleneproducts separation plant streams may be used as heat sources in theheat recovery circuit 102, along with other plants such as the benzeneextraction unit, CCR, and xylene isomerization reaction and separationsections.

Heat exchangers 103 a-103 c recover heat from heat sources in arefining-petrochemicals complex portion that contains the para-xyleneseparation unit. Together, the heat exchangers in the heat recoverycircuit 103 recover low grade waste heat to deliver the heat via theworking fluid to the ORC 104 a. In this example, the heat from heatrecovery circuit 103 is provided to an evaporator 108 a of the ORC 104a.

Generally, the heat recovery circuit 103 receives (for example, from aninlet header that fluidly couples a heating fluid tank 118 to the heatexchangers 103 a-103 c) high pressure working fluid (for example, hotwater, hot oil, or otherwise) at or about 100-110° C. and it heats it upto about 125-160° C. The heat exchangers 103 a-103 c may be distributedalong the CCR-Aromatics module of the refining-petrochemical complexusing low grade waste heat sources in the refining-petrochemical complexplants using only para-xylene products separation plant streams.

Heat exchangers 105 a-105 g in heat recovery circuit 105, in thisexample, recover heat from heat sources in a hydrocracking plantseparation unit. Heat exchangers 105 h-105 j in heat recovery circuit105, in this example, recover heat from heat sources in a hydrotreatingplant separation unit. Together, the heat exchangers in the heatrecovery circuit 105 recover low grade waste heat to deliver the heatvia the working fluid to an ORC 104 b. In this example, the heat fromheat recovery circuit 105 is provided to an evaporator 108 b of the ORC104 b.

Generally, the heat recovery circuit 105 receives (for example, from aninlet header that fluidly couples the heating fluid tank 116 to the heatexchangers 105 a-105 j) high pressure working fluid (for example, hotwater, hot oil, or otherwise) at or about 40-60° C. and it heats it upto about 120-160° C.

In the example implementation of system 100, the ORC 104 a includes aworking fluid that is thermally coupled to the heat recovery circuits102 and 103 to heat the working fluid. In some implementations, theworking fluid can be isobutane. The ORC 104 a can also include a gasexpander 110 a (for example, a turbine-generator) configured to generateelectrical power from the heated working fluid. As shown in FIG. 1A, theORC 104 a can additionally include a pre-heater 106 a, an evaporator 108a, a pump 114 a, and a condenser 112 a. In this example implementation,the heat recovery circuit 102 supplies a heated working, or heating,fluid to the pre-heater 106 a, while the heat recovery circuit 103supplies a heated working, or heating, fluid to the evaporator 108 a.

In the example implementation of system 100, the ORC 104 b includes aworking fluid that is thermally coupled to the heat recovery circuit 105to heat the working fluid. In some implementations, the working fluidcan be isobutane. The ORC 104 b can also include a gas expander 110 b(for example, a turbine-generator) configured to generate electricalpower from the heated working fluid. As shown in FIG. 1B, the ORC 104 bcan additionally include an evaporator 108 b, a pump 114 b, and acondenser 114 b. In this example implementation, the heat recoverycircuit 105 supplies a heated working, or heating, fluid to theevaporator 108 b.

In a general operation, a working, or heating, fluid (for example,water, oil, or other fluid) is circulated through the heat exchangers ofthe heat recovery circuits 102, 103, and 105. An inlet temperature ofthe heating fluid that is circulated into the inlets of each of the heatexchangers may be the same or substantially the same subject to anytemperature variations that may result as the heating fluid flowsthrough respective inlets, and may be circulated directly from a heatingfluid tank 116 or 118. Each heat exchanger heats the heating fluid to arespective temperature that is greater than the inlet temperature. Theheated heating fluids from the heat exchangers are combined in theirrespective heat recovery circuits and circulated through one of thepre-heater 106 a, the evaporator 108 a, or the evaporator 108 b of theORC. Heat from the heated heating fluid heats the working fluid of therespective ORC thereby increasing the working fluid pressure andtemperature. The heat exchange with the working fluid results in adecrease in the temperature of the heating fluid. The heating fluid isthen collected in the heating fluid tank 116 or the heating fluid tank118 and can be pumped back through the respective heat exchangers torestart the waste heat recovery cycle.

The heating fluid circuit to flow heating fluid through the heatexchangers of system 100 can include multiple valves that can beoperated manually or automatically. For example, a modulating controlvalve (as one example) may be positioned in fluid communication with aninlet or outlet of each heat exchanger, on the working fluid and heatsource side. In some aspects, the modulating control valve may be ashut-off valve or additional shut-off valves may also be positioned influid communication with the heat exchangers. An operator can manuallyopen each valve in the circuit to cause the heating fluid to flowthrough the circuit. To cease waste heat recovery, for example, toperform repair or maintenance or for other reasons, the operator canmanually close each valve in the circuit. Alternatively, a controlsystem, for example, a computer-controlled control system, can beconnected to each valve in the circuit. The control system canautomatically control the valves based, for example, on feedback fromsensors (for example, temperature, pressure or other sensors), installedat different locations in the circuit. The control system can also beoperated by an operator.

In the manner described earlier, the heating fluid can be looped throughthe heat exchangers to recover heat that would otherwise go to waste inthe hydrocracking, hydrotreating, CCR, and aromatics plants, and to usethe recovered waste heat to operate the power generation system. Bydoing so, an amount of energy needed to operate the power generationsystem can be decreased while obtaining the same or substantiallysimilar power output from the power generation system. For example, thepower output from the power generation system that implements the wasteheat recovery network can be higher or lower than the power output fromthe power generation system that does not implement the waste heatrecovery network. Where the power output is less, the difference may notbe statistically significant. Consequently, a power generationefficiency of the petrochemical refining system can be increased.

FIG. 1C is a schematic diagram that illustrates an example placement ofheat exchanger 102 g in a crude oil refinery continuous catalyticreforming (CCR) plant. In an example implementation illustrated in FIGS.1C and 1T, this heat exchanger 102 g may cool down the CCR last stagereactor outlet after the feed-effluent heat exchanger stream from 111°C. to 60° C. using the high pressure working fluid stream of the heatrecovery circuit 102 at 50° C. to raise the working fluid temperature to106° C. The thermal duty of this heat exchanger 102 g may be about 38.9MW. The heating fluid stream at 106° C. is sent to the header of heatrecovery circuit 102.

FIG. 1D is a schematic diagram that illustrates an example placement ofheat exchangers 102 h and 102 i in the crude oil refinery continuouscatalytic reforming (CCR) plant. In an example implementationillustrated in FIGS. 1D and 1S, these two heat exchangers 102 h and 102i have thermal duties of 7.75 MW and 9.29 MW, respectively. Heatexchanger 102 h cools down a 1st stage compressor outlet stream from135° C. to 60° C. using the working fluid stream of heat recoverycircuit 102 at 50° C. to raise its temperature to 130° C. The heatingfluid stream at 130° C. is sent to the header of heat recovery circuit102. The heat exchanger 102 i cools down a 2nd stage compressor outletstream from 143° C. to 60° C. using the working fluid stream of heatrecovery circuit 102 at 50° C. to raise its temperature to 138° C. Theheating fluid stream at 138° C. is sent to the header of heat recoverycircuit 102.

FIG. 1G is a schematic diagram that illustrates an example placement ofheat exchanger 102 j in the crude oil refinery continuous catalyticreforming (CCR) plant. In an example implementation illustrated in FIGS.1G and 1S, this heat exchanger 102 j cools down the CCR light reformatesplitter column overhead stream from 87° C. to 60° C. using the workingfluid stream of heat recovery circuit 102 at 50° C. to raise the workingfluid stream temperature to 82° C. The thermal duty of this heatexchanger 102 j is about 24.1 MW. The heating fluid at 82° C. is sent tothe header of heat recovery circuit 102.

FIG. 1F is a schematic diagram that illustrates an example placement ofheat exchanger 102 f in the benzene extraction unit. In an exampleimplementation illustrated in FIGS. 1F and 1S, this heat exchanger 102 fcools down an overhead stream from 104° C. to 100° C. using the workingfluid stream of heat recovery circuit 102 at 50° C. to raise the workingfluid stream temperature to 99° C. The thermal duty of this heatexchanger 102 f is 4.99 MW. The heating fluid at 99° C. is sent to theheader of heat recovery circuit 102.

FIG. 1G is a schematic diagram that illustrates an example placement ofheat exchanger 102 d in the Para-Xylene separation plant. In an exampleimplementation illustrated in FIGS. 1G and 1S, this heat exchanger 102 dcools down the Xylene isomerization reactor outlet stream before theseparator drum from 114° C. to 60° C. using the working fluid stream ofheat recovery circuit 102 at 50° C. to raise the working fluid streamtemperature to 109° C. The thermal duty of this heat exchanger 102 d isabout 15.6 MW. The heating fluid at 109° C. is sent to the header ofheat recovery circuit 102.

FIG. 1H is a schematic diagram that illustrates an example placement ofheat exchanger 102 e in the xylene isomerization de-heptanizer of thePara-Xylene separation plant. In an example implementation illustratedin FIGS. 1H and 1S, this heat exchanger 102 e cools down thede-heptanizer column overhead stream from 112° C. to 60° C. using theworking fluid stream of heat recovery circuit 102 at 50° C. to raise theworking fluid stream temperature to 107° C. The thermal duty of thisheat exchanger 102 e is about 21 MW. The heating fluid at 107° C. issent to the header of heat recovery circuit 102.

FIG. 1I is a schematic diagram that illustrates an example placement ofheat exchanger 103 a in the Para-Xylene separation plant. In an exampleimplementation illustrated in FIGS. 1I and 1S, this heat exchanger 103 acools down an extract column overhead stream from 156° C. to 133° C.using the working fluid stream of heat recovery circuit 103 at 105° C.to raise the working fluid stream temperature to 151° C. The thermalduty of this heat exchanger 103 a is about 33 MW. The heating fluid at151° C. is sent to the header of heat recovery circuit 103.

FIG. 1J is a schematic diagram that illustrates an example placement ofheat exchanger 102 b in the Para-Xylene separation plant. In an exampleimplementation illustrated in FIGS. 1J and 1S, this heat exchanger 102 bcools down the PX purification column bottom product stream from 155° C.to 60° C. using the working fluid stream of heat recovery circuit 102 at50° C. to raise the working fluid stream temperature to 150° C. Thethermal duty of this heat exchanger 102 b is about 5.16 MW. The heatingfluid at 150° C. is sent to the header of heat recovery circuit 102.

FIG. 1K is a schematic diagram that illustrates an example placement ofheat exchanger 102 a in the Para-Xylene separation plant. In an exampleimplementation illustrated in FIGS. 1K and 1S, this heat exchanger 102 acools down the PX purification column overhead stream from 127° C. to84° C. using the working fluid stream of heat recovery circuit 102 at50° C. to raise the working fluid stream temperature to 122° C. Thethermal duty of this heat exchanger 102 a is about 13.97 MW. The heatingfluid at 122° C. is sent to the header of heat recovery circuit 102.

FIG. 1L is a schematic diagram that illustrates an example placement ofheat exchanger 103 b in the Para-Xylene separation plant. In an exampleimplementation illustrated in FIGS. 1L and 1S, this heat exchanger 103 bcools down a Raffinate column overhead stream from 162° C. to 130° C.using the working fluid stream of heat recovery circuit 103 at 105° C.to raise the working fluid stream temperature to 157° C. The thermalduty of this heat exchanger 103 b is about 91.1 MW. The heating fluid at157° C. is sent to the header of heat recovery circuit 103.

FIG. 1M is a schematic diagram that illustrates an example placement ofheat exchangers 102 c and 103 c in the Para-Xylene separation plant. Inan example implementation illustrated in FIGS. 1M and 1S, these two heatexchangers 102 c and 103 c have thermal duties of 7.23 MW and 32.46 MW,respectively. Heat exchanger 102 c cools down the C9+ aromatics beforethe storage tank from 169° C. to 60° C. using the working fluid streamof heat recovery circuit 102 at 50° C. to raise its temperature to 164°C. The heating fluid stream at 164° C. is sent to the header of heatrecovery circuit 102. The heat exchanger 103 c cools down the heavyRaffinate splitter column overhead stream from 126° C. to 113° C. usingthe working fluid stream of heat recovery circuit 103 at 105° C. toraise its temperature to 121° C. The heating fluid stream at 121° C. issent to the header of heat recovery circuit 103.

FIG. 1N is a schematic diagram that illustrates an example placement ofheat exchanger 105 a in the hydrocracking plant. In an exampleimplementation illustrated in FIGS. 1N and 1T, this heat exchanger 105 acools down the 2nd reaction section 2nd stage cold high pressureseparator feed stream from 157° C. to 60° C. using the working fluidstream of heat recovery circuit 105 at 50° C. to raise the working fluidstream temperature to 152° C. The thermal duty of this heat exchanger105 a is about 26.25 MW. The heating fluid at 152° C. is sent to theheader of heat recovery circuit 105.

FIG. 1O is a schematic diagram that illustrates an example placement ofheat exchanger 105 b in the hydrocracking plant. In an exampleimplementation illustrated in FIGS. 1O and 1T, this heat exchanger 105 bcools down the 1st reaction section 1st stage cold high pressureseparator feed stream from 159° C. to 60° C. using the working fluidstream of heat recovery circuit 105 at 50° C. to raise the working fluidstream temperature to 152° C. The thermal duty of this heat exchanger105 b is about 81.51 MW. The heating fluid at 152° C. is sent to theheader of heat recovery circuit 105.

FIGS. 1PA and 1PB illustrates a schematic diagram that illustrates anexample placement of heat exchangers 105 c-105 g in the hydrocrackingplant. In an example implementation illustrated in FIGS. 1PA-1PB and 1S,these heat exchangers 105 c-105 g have thermal duties of 36.8 MW, 89 MW,19.5 MW, 4.65 MW, and 5.74 MW, respectively. Heat exchanger 105 c coolsdown the product stripper overhead stream from 169° C. to 60° C. usingthe working fluid stream of heat recovery circuit 105 at 50° C. to raiseits temperature to 164° C. The heating fluid stream at 164° C. is sentto the header of heat recovery circuit 105. The heat exchanger 105 dcools down the main fractionator overhead stream from 136° C. to 60° C.using the working fluid stream of heat recovery circuit 105 at 50° C. toraise its temperature to 131° C. The heating fluid stream at 131° C. issent to the header of heat recovery circuit 105. The heat exchanger 105e cools down the kerosene product stream from 160° C. to 60° C. usingthe working fluid stream of heat recovery circuit 105 at 50° C. to raiseits temperature to 155° C. The heating fluid stream at 155° C. is sentto the header of heat recovery circuit 105. In an example aspect, asteam generator with a thermal duty of about 5.45 MW using a hot streamtemperature of 187° C. is used before this heat exchanger 105 e togenerate low pressure steam for process use. The heat exchanger 105 fcools down the kerosene pumparound stream from 160° C. to 60° C. usingthe working fluid stream of heat recovery circuit 105 at 50° C. to raiseits temperature to 155° C. The heating fluid stream at 155° C. is sentto the header of heat recovery circuit 105. In an example aspect, asteam generator with a thermal duty of about 5.58 MW using a hot streamtemperature of 196° C. is used before this heat exchanger 105 f togenerate low pressure steam for process use. The heat exchanger 105 gcools down the diesel product stream from 160° C. to 60° C. using theworking fluid stream of heat recovery circuit 105 at 50° C. to raise itstemperature to 155° C. The heating fluid stream at 155° C. is sent tothe header of heat recovery circuit 105. In an example aspect, a steamgenerator with a thermal duty of about 6.47 MW using a hot streamtemperature of 204° C. is used before this heat exchanger 105 g togenerate low pressure steam for process use.

FIG. 1Q is a schematic diagram that illustrates an example placement ofheat exchanger 105 h in the hydrotreating plant. In an exampleimplementation illustrated in FIGS. 1Q and 1T, this heat exchanger 105 hcools down the light effluent to cold separator stream from 127° C. to60° C. using the working fluid stream of heat recovery circuit 105 at50° C. to raise the working fluid stream temperature to 122° C. Thethermal duty of this heat exchanger 105 h is about 23.4 MW. The heatingfluid at 122° C. is sent to the header of heat recovery circuit 105.

FIG. 1R is a schematic diagram that illustrates an example placement ofheat exchangers 105 i and 105 j in the hydrotreating plant. In anexample implementation illustrated in FIGS. 1R and 1T, these heatexchangers have thermal duties of 33.58 MW and 60.71 MW, respectively.The heat exchanger 105 i cools down the diesel stripper overhead streamfrom 160° C. to 60° C. using the working fluid stream of heat recoverycircuit 105 at 50° C. to raise the working fluid stream temperature to155° C. The heating fluid at 155° C. is sent to the header of heatrecovery circuit 105. In an example aspect, a steam generator with athermal duty of about 6.38 MW using an overhead hot stream temperatureof 182° C. is used before this heat exchanger 105 i to generate lowpressure steam for process use. The heat exchanger 105 i cools down thediesel stripper product stream from 162° C. to 60° C. using the workingfluid stream of heat recovery circuit 105 at 50° C. to raise the workingfluid stream temperature to 157° C. The heating fluid at 157° C. is sentto the header of heat recovery circuit 105.

As described earlier, FIGS. 1S-1T illustrate a specific example of thesystem 100, including some example temperatures, thermal duties,efficiencies, power inputs, and power outputs. For example, asillustrated in FIG. 1S, the CCR-Aromatics module generates a poweroutput (with a gas turbine 110 a using efficiency of 85%) of about 37.5MW and the power consumed in the pump using efficiency of 75% is about2.9 MW. The ORC 104 a high pressure at the inlet of the turbine is about20 bar and at the outlet is about 4.3 bar. The condenser 112 a watersupply temperature is assumed to be at 20° C. and return temperature isassumed to be at 30° C. The evaporator 108 a thermal duty is about 157MW to vaporize about 745 Kg/s of isobutane. The ORC 104 a isobutanepre-heater 106 a thermal duty is about 147 MW to heat up the isobutanefrom about 31° C. to 99° C. The condenser 112 a cooling duty is 269 MWto cool down and condense the same flow of isobutane from about 52° C.to 30° C.

As illustrated in FIG. 1T, the Hydrocracking-Diesel Hydrotreating modulegenerates about 45 MW (with the gas turbine 110 b using efficiency of85%), and the power consumed in the pump 114 b using efficiency of 75%is about 3.5 MW. The ORC 104 b high pressure at the inlet of the turbine110 b is about 20 bar and at the outlet is about 4.3 bar. The condenser112 b water supply temperature is assumed to be at 20° C. and returntemperature is assumed to be at 30° C. The evaporator 108 b thermal dutyis about 363 MW to pre-heat and vaporize about 887 Kg/s of isobutanefrom about 31° C. to 99° C., and the condenser 112 b cooling duty isabout 321 MW to cool down and condense the same flow of isobutane fromabout 52° C. to 30° C.

FIG. 1U is a graph that shows a tube side fluid temperature (forexample, a cooling, or condenser, fluid flow) and a shell side fluidtemperature (for example, an ORC working fluid flow) in the condensers112 a and 112 b during an operation of the system 100. This graph showsa temperature difference between the fluids on the y-axis relative to aheat flow between the fluids on the x-axis. For example, as shown inthis figure, as the temperature difference between the fluids decreases,a heat flow between the fluids can increase. In some aspects, thecooling fluid medium may be at or about 20° C. or even higher. In suchcases, a gas expander outlet pressure (for example, pressure of the ORCworking fluid exiting the gas expander) may be high enough to allow thecondensation of the ORC working fluid at the available cooling fluidtemperature. As shown in FIG. 1U, the condenser water (entering thetubes of the condensers 112 a and 112 b) enters at about 20° C. andleaves at about 30° C. The ORC working fluid (entering the shell-side ofthe condensers) enters as a vapor at about 52° C., and then condenses at30° C. and leaves the condensers as a liquid at 30° C.

FIG. 1V is a graph that shows a tube side fluid temperature (forexample, a heating fluid flow) and a shell side fluid temperature (forexample, an ORC working fluid flow) in the evaporator 108 a during anoperation of the system 100. This graph shows a temperature differencebetween the fluids on the y-axis relative to a heat flow between thefluids on the x-axis. For example, as shown in this figure, as thetemperature difference between the fluids decreases, a heat flow betweenthe fluids can increase. For example, as shown in FIG. 1V, as thetube-side fluid (for example, the hot oil or water in the heating fluidcircuit 103) is circulated through the evaporator 108 a, heat istransferred from that fluid to the shell-side fluid (for example, theORC working fluid). Thus, the tube-side fluid enters the evaporator 108a at about 141° C. and leaves the evaporator 108 a at about 105° C. Theshell-side fluid enters the evaporator 108 a, from the pre-heater 106 a,at about 99° C. (for example, as a liquid or mixed phase fluid) andleaves the evaporator 108 a also at about 99° C. (for example, as avapor with some superheating).

FIG. 1W is a graph that shows a tube side fluid temperature (forexample, a heating fluid flow) and a shell side fluid temperature (forexample, an ORC working fluid flow) in the evaporator 108 b during anoperation of the system 100. This graph shows a temperature differencebetween the fluids on the y-axis relative to a heat flow between thefluids on the x-axis. For example, as shown in this figure, as thetemperature difference between the fluids decreases, a heat flow betweenthe fluids can increase. As shown in FIG. 1W, as the tube-side fluid(for example, the hot oil or water in the heating fluid circuit 105) iscirculated through the evaporator 108 b, heat is transferred from thatfluid to the shell-side fluid (for example, the ORC working fluid).Thus, the tube-side fluid enters the evaporator 108 b at about 140° C.and leaves the evaporator 108 b at about 105° C. The shell-side fluidenters the evaporator 108 b at about 30° C. (for example, as a liquid)and leaves the evaporator 108 b at about 99° C. (for example, as avapor). The graph in FIG. 1W includes a “pinch point” for the shell-sidefluid (for example, the ORC working fluid). The pinch point, whichoccurs as the fluid reaches about 99° C., represents the temperature atwhich the shell-side fluid vaporizes. As the shell-side fluid continuesthrough the respective evaporator, the fluid temperature remainssubstantially constant (that is, about 99° C.) as the fluid completevaporizes and, in some aspects, becomes superheated.

FIG. 1X is a graph that show a tube-side fluid temperature (for example,a heating fluid flow) and a shell-side fluid temperature (for example,an ORC working fluid flow) in the pre-heater 106 a during an operationof the system 100. This graph shows a temperature difference between thefluids on the y-axis relative to a heat flow between the fluids on thex-axis. For example, as shown in this figure, as the temperaturedifference between the fluids decreases, a heat flow between the fluidscan increase. This graph shows a temperature difference between thefluids on the y-axis relative to a heat flow between the fluids on thex-axis. For example, as shown in FIG. 1X, as the tube-side fluid (forexample, the hot oil or water in the heating fluid circuit 102) iscirculated through the pre-heater 106 a, heat is transferred from thatfluid to the shell-side fluid (for example, the ORC working fluid).Thus, the tube-side fluid enters the pre-heater 106 a at about 105° C.and leaves the pre-heater 106 a at about 50° C. The shell-side fluidenters the pre-heater 106 a at about 30° C. (for example, as a liquid)and leaves the pre-heater 106 a at about 99° C. (for example, also as aliquid or mixed phase fluid).

In the illustrated example, system 100 may include two-independentmodules-based power generation using a dieselhydrotreating-hydrocracking plant module and acontinuous-catalytic-cracking-aromatics plant module for a more energyefficient and “greener” configuration in refining-petrochemical complexvia converting its low-low grade waste heat to net power by about 76 MWfor local utilization or export to the national electricity grid. System100 may facilitate the reduction in power-generation-based GHG emissionswith desired operability due to the independent nature of the twomodules in the scheme.

The techniques to recover heat energy generated by a petrochemicalrefining system described above can be implemented in at least one orboth of two example scenarios. In the first scenario, the techniques canbe implemented in a petrochemical refining system that is to beconstructed. For example, a geographic layout to arrange multiplesub-units of a petrochemical refining system can be identified. Thegeographic layout can include multiple sub-unit locations at whichrespective sub-units are to be positioned. Identifying the geographiclayout can include actively determining or calculating the location ofeach sub-unit in the petrochemical refining system based on particulartechnical data, for example, a flow of petrochemicals through thesub-units starting from crude petroleum and resulting in refinedpetroleum. Identifying the geographic layout can alternatively or inaddition include selecting a layout from among multiplepreviously-generated geographic layouts. A first subset of sub-units ofthe petrochemical refining system can be identified. The first subsetcan include at least two (or more than two) heat-generating sub-unitsfrom which heat energy is recoverable to generate electrical power. Inthe geographic layout, a second subset of the multiple sub-unitlocations can be identified. The second subset includes at least twosub-unit locations at which the respective sub-units in the first subsetare to be positioned. A power generation system to recover heat energyfrom the sub-units in the first subset is identified. The powergeneration system can be substantially similar to the power generationsystem described earlier. In the geographic layout, a power generationsystem location can be identified to position the power generationsystem. At the identified power generation system location, a heatenergy recovery efficiency is greater than a heat energy recoveryefficiency at other locations in the geographic layout. Thepetrochemical refining system planners and constructors can performmodeling and/or computer-based simulation experiments to identify anoptimal location for the power generation system to maximize heat energyrecovery efficiency, for example, by minimizing heat loss whentransmitting recovered heat energy from the at least two heat-generatingsub-units to the power generation system. The petrochemical refiningsystem can be constructed according to the geographic layout bypositioning the multiple sub-units at the multiple sub-unit locations,positioning the power generation system at the power generation systemlocation, interconnecting the multiple sub-units with each other suchthat the interconnected multiple sub-units are configured to refinepetrochemicals, and interconnecting the power generation system with thesub-units in the first subset such that the power generation system isconfigured to recover heat energy from the sub-units in the first subsetand to provide the recovered heat energy to the power generation system.The power generation system is configured to generate power using therecovered heat energy.

In the second scenario, the techniques can be implemented in anoperational petrochemical refining system. In other words, the powergeneration system described earlier can be retrofitted to an alreadyconstructed and operational petrochemical refining system.

In summary, this disclosure describes configurations and relatedprocessing schemes of mini-power plants synthesized for grassrootsmedium grade crude oil semi-conversion refineries to generate power fromspecific portions of low grade waste heat sources. The disclosure alsodescribes configurations and related processing schemes of mini-powerplants synthesized for integrated medium grade crude oil semi-conversionrefineries and aromatics complex for power generation from specificportions of low grade waste sources.

The economics of industrial production, the limitations of global energysupply, and the realities of environmental conservation are concerns forall industries. It is believed that the world's environment has beennegatively affected by global warming caused, in part, by the release ofGHG into the atmosphere. Implementations of the subject matter describedhere can alleviate some of these concerns, and, in some cases, preventcertain refineries, which are having difficulty in reducing their GHGemissions, from having to shut down. By implementing the techniquesdescribed here, specific plants in a refinery or a refinery, as a whole,can be made more efficient and less polluting by carbon-free powergeneration from specific portions of low grade waste heat sources.

Thus, particular implementations of the subject matter have beendescribed. Other implementations are within the scope of the followingclaims.

What is claimed is:
 1. A power generation system, comprising: a firstheating fluid circuit thermally coupled to a first plurality of heatsources from a first plurality of sub-units of a petrochemical refiningsystem, the first plurality of sub-units comprising a continuouscatalytic reforming (CCR) and aromatics refining system; a secondheating fluid circuit thermally coupled to a second plurality of heatsources of a second plurality of sub-units of the petrochemical refiningsystem, the second plurality of sub-units comprising the CCR andaromatics refining system; a third heating fluid circuit thermallycoupled to a third plurality of heat sources from a third plurality ofsub-units of the petrochemical refining system, the third plurality ofsub-units comprising a hydrocracking-diesel hydrotreating system; afirst power generation system that comprises a first organic Rankinecycle (ORC), the first ORC comprising (i) a first working fluid that isthermally coupled to the first and second heating fluid circuits to heatthe first working fluid, and (ii) a first expander configured togenerate electrical power from the heated first working fluid; a secondpower generation system that comprises a second ORC, the second ORCcomprising (i) a second working fluid that is thermally coupled to thethird heating fluid circuit to heat the second working fluid, and (ii) asecond expander configured to generate electrical power from the heatedsecond working fluid; and a control system configured to actuate a firstset of control valves to selectively thermally couple the first heatingfluid circuit to at least a portion of the first plurality of heatsources, the control system also configured to actuate a second set ofcontrol valves to selectively thermally couple the second heating fluidcircuit to at least a portion of the second plurality of heat sources,the control system also configured to actuate a third set of controlvalves to selectively thermally couple the third heating fluid circuitto at least a portion of the third plurality of heat sources.
 2. Thepower generation system of claim 1, wherein the first working fluid isthermally coupled to the first heating fluid circuit in a pre-heatingheat exchanger of the first ORC, and the first working fluid isthermally coupled to the second heating fluid circuit in an evaporatorof the first ORC.
 3. The power generation system of claim 1, wherein thefirst heating fluid circuit comprises a first heating fluid tank that isfluidly coupled to the first and third heating fluid circuits and thepre-heating heat exchanger of the first ORC, and the second heatingfluid circuit comprises a second heating fluid tank that is fluidlycoupled with the evaporator of the first ORC.
 4. The power generationsystem of claim 1, wherein the second working fluid is thermally coupledto the third heating fluid circuit in an evaporator of the second ORC.5. The power generation system of claim 1, wherein at least one of thefirst or second working fluids comprises isobutane.
 6. The powergeneration system of claim 1, wherein at least one of the first, second,or third heating fluid circuits comprises water or oil.
 7. The powergeneration system of claim 1, wherein the first ORC further comprises: acondenser fluidly coupled to a condenser fluid source to cool the firstworking fluid and a pump to circulate the first working fluid throughthe first ORC, and the second ORC further comprises a condenser fluidlycoupled to the condenser fluid source to cool the second working fluidand a pump to circulate the second working fluid through the second ORC.8. The power generation system of claim 1, wherein a first sub-set ofthe first plurality of heat sources comprises at least three para-xyleneseparation unit heat sources, comprising: a first para-xylene separationunit heat source comprising a heat exchanger that is fluidly coupled toa raw paraxylene stream circulated through an air cooler to a storagetank, and is fluidly coupled to the first heating fluid circuit, asecond para-xylene separation unit heat source comprising a heatexchanger that is fluidly coupled to a paraxylene purification streamcirculated through an air cooler to a paraxylene purification refluxdrum, and is fluidly coupled to the first heating fluid circuit, and athird para-xylene separation unit heat source comprising a heatexchanger that is fluidly coupled to a C9+ARO stream circulated throughan air cooler to a C9+ARO storage, and is fluidly coupled to the firstheating fluid circuit; a second sub-set of the first plurality of heatsources comprises at least two para-xylene separation-xyleneisomerization reaction and separation unit heat sources, comprising: afirst para-xylene separation-xylene isomerization reaction andseparation unit heat source comprising a heat exchanger that is fluidlycoupled to a Xylene isomerization reactor outlet stream before aseparator drum, and is fluidly coupled to the first heating fluidcircuit, and a second para-xylene separation-xylene isomerizationreaction and separation unit heat source comprising a heat exchangerthat is fluidly coupled to a de-heptanizer column overhead stream, andis fluidly coupled to the first heating fluid circuit; a third sub-setof the first plurality of heat sources comprises an aromaticscomplex-benzene extraction unit heat source comprising a heat exchangerthat is fluidly coupled to an overhead stream, and is fluidly coupled tothe first heating fluid circuit; and a fourth sub-set of the firstplurality of heat sources comprises at least four continuous catalyticcracking heat sources, comprising: a first continuous catalytic crackingheat source comprising a heat exchanger that is fluidly coupled to a CCRlast stage reactor outlet after a feed-effluent heat exchanger stream,and is fluidly coupled to the first heating fluid circuit, a secondcontinuous catalytic cracking heat source comprising a heat exchangerthat is fluidly coupled to a 1st stage compressor outlet stream, and isfluidly coupled to the first heating fluid circuit, a third continuouscatalytic cracking heat source comprising a heat exchanger that isfluidly coupled to a 2nd stage compressor outlet stream, and is fluidlycoupled to the first heating fluid circuit, and a fourth continuouscatalytic cracking heat source comprising a heat exchanger that isfluidly coupled to a CCR light reformate splitter column overheadstream, and is fluidly coupled to the first heating fluid circuit. 9.The power generation system of claim 8, wherein a first sub-set of thesecond plurality of heat sources comprises at least three para-xyleneseparation unit heat sources, comprising: a first para-xylene separationunit heat source comprising a heat exchanger that is fluidly coupled toan extract column overhead stream, and is fluidly coupled to the secondheating fluid circuit, a second para-xylene separation unit heat sourcecomprising a heat exchanger that is fluidly coupled to a Raffinatecolumn overhead stream, and is fluidly coupled to the second heatingfluid circuit, and a third para-xylene separation unit heat sourcecomprising a heat exchanger that is fluidly coupled to a heavy Raffinatesplitter column overhead stream, and is fluidly coupled to the secondheating fluid circuit.
 10. The power generation system of claim 9,wherein a first sub-set of the third plurality of heat sources comprisesat least three diesel hydrotreating reaction and stripping heat sources,comprising: a first diesel hydrotreating reaction and stripping heatsource comprising a heat exchanger that is fluidly coupled to a lighteffluent to cold separator stream, and is fluidly coupled to the thirdheating fluid circuit, a second diesel hydrotreating reaction andstripping heat source comprising a heat exchanger that is fluidlycoupled to a diesel stripper overhead stream, and is fluidly coupled tothe third heating fluid circuit, a third diesel hydrotreating reactionand stripping heat source comprising a heat exchanger that is fluidlycoupled to a diesel stripper product stream, and is fluidly coupled tothe third heating fluid circuit; and a second sub-set of the thirdplurality of heat sources comprises at least seven hydrocracking plantheat sources, comprising: a first hydrocracking plant heat sourcecomprising a heat exchanger that is fluidly coupled to a 2nd reactionsection 2nd stage cold high pressure separator feed stream, and isfluidly coupled to the third heating fluid circuit, a secondhydrocracking plant heat source comprising a heat exchanger that isfluidly coupled to a 1st reaction section 1st stage cold high pressureseparator feed stream, and is fluidly coupled to the third heating fluidcircuit, a third hydrocracking plant heat source comprising a heatexchanger that is fluidly coupled to a product stripper overhead stream,and is fluidly coupled to the third heating fluid circuit, a fourthhydrocracking plant heat source comprising a heat exchanger that isfluidly coupled to a main fractionator overhead stream, and is fluidlycoupled to the third heating fluid circuit, a fifth hydrocracking plantheat source comprising a heat exchanger that is fluidly coupled to akerosene product stream, and is fluidly coupled to the third heatingfluid circuit, a sixth hydrocracking plant heat source comprising a heatexchanger that is fluidly coupled to a kerosene pumparound stream, andis fluidly coupled to the third heating fluid circuit, and a seventhhydrocracking plant heat source comprises a heat exchanger that isfluidly coupled to a diesel product stream, and is fluidly coupled tothe third heating fluid circuit.
 11. A method of recovering heat energygenerated by a petrochemical refining system, the method comprising:circulating a first heating fluid through a first heating fluid circuitthermally coupled to a first plurality of heat sources from a firstplurality of sub-units of a petrochemical refining system, the firstplurality of sub-units comprising a continuous catalytic reforming (CCR)and aromatics refining system; circulating a second heating fluidthrough a second heating fluid circuit thermally coupled to a secondplurality of heat sources of a second plurality of sub-units of thepetrochemical refining system, the second plurality of sub-unitscomprising the CCR and aromatics refining system; circulating a thirdheating fluid through a third heating fluid circuit thermally coupled toa third plurality of heat sources from a third plurality of sub-units ofthe petrochemical refining system, the third plurality of sub-unitscomprising a hydrocracking-diesel hydrotreating system; generatingelectrical power through a first power generation system that comprisesa first organic Rankine cycle (ORC), the first ORC comprising (i) afirst working fluid that is thermally coupled to the first and secondheating fluid circuits to heat the first working fluid with the firstand second heating fluids, and (ii) a first expander configured togenerate electrical power from the heated first working fluid;generating electrical power through a second power generation systemthat comprises a second ORC, the second ORC comprising (i) a secondworking fluid that is thermally coupled to the third heating fluidcircuit to heat the second working fluid with the third heating fluid,and (ii) a second expander configured to generate electrical power fromthe heated second working fluid; actuating, with a control system, afirst set of control valves to selectively thermally couple the firstheating fluid circuit to at least a portion of the first plurality ofheat sources to heat the first heating fluid with the first plurality ofheat sources; actuating, with the control system, a second set ofcontrol valves to selectively thermally couple the second heating fluidcircuit to at least a portion of the second plurality of heat sources toheat the second heating fluid with the second plurality of heat sources;and actuating, with the control system, a third set of control valves toselectively thermally couple the third heating fluid circuit to at leasta portion of the third plurality of heat sources to heat the thirdheating fluid with the third plurality of heat sources.
 12. The methodof claim 11, wherein the first working fluid is thermally coupled to thefirst heating fluid circuit in a pre-heating heat exchanger of the firstORC, and the first working fluid is thermally coupled to the secondheating fluid circuit in an evaporator of the first ORC.
 13. The methodof claim 11, wherein the first heating fluid circuit comprises a firstheating fluid tank that is fluidly coupled to the first and thirdheating fluid circuits and the pre-heating heat exchanger of the firstORC, and the second heating fluid circuit comprises a second heatingfluid tank that is fluidly coupled with the evaporator of the first ORC.14. The method of claim 11, wherein the second working fluid isthermally coupled to the third heating fluid circuit in an evaporator ofthe second ORC.
 15. The method of claim 11, wherein at least one of thefirst or second working fluids comprises isobutane.
 16. The method ofclaim 11, wherein at least one of the first, second, or third heatingfluid circuits comprises water or oil.
 17. The method of claim 11,wherein the first ORC further comprises: a condenser fluidly coupled toa condenser fluid source to cool the first working fluid and a pump tocirculate the first working fluid through the first ORC, and the secondORC further comprises a condenser fluidly coupled to the condenser fluidsource to cool the second working fluid and a pump to circulate thesecond working fluid through the second ORC.
 18. The method of claim 11,wherein a first sub-set of the first plurality of heat sources comprisesat least three para-xylene separation unit heat sources, comprising: afirst para-xylene separation unit heat source comprising a heatexchanger that is fluidly coupled to a raw paraxylene stream circulatedthrough an air cooler to a storage tank, and is fluidly coupled to thefirst heating fluid circuit, a second para-xylene separation unit heatsource comprising a heat exchanger that is fluidly coupled to aparaxylene purification stream circulated through an air cooler to aparaxylene purification reflux drum, and is fluidly coupled to the firstheating fluid circuit, and a third para-xylene separation unit heatsource comprising a heat exchanger that is fluidly coupled to a C9+AROstream circulated through an air cooler to a C9+ARO storage, and isfluidly coupled to the first heating fluid circuit; a second sub-set ofthe first plurality of heat sources comprises at least two para-xyleneseparation-xylene isomerization reaction and separation unit heatsources, comprising: a first para-xylene separation-xylene isomerizationreaction and separation unit heat source comprising a heat exchangerthat is fluidly coupled to a Xylene isomerization reactor outlet streambefore a separator drum, and is fluidly coupled to the first heatingfluid circuit, and a second para-xylene separation-xylene isomerizationreaction and separation unit heat source comprising a heat exchangerthat is fluidly coupled to a de-heptanizer column overhead stream, andis fluidly coupled to the first heating fluid circuit; a third sub-setof the first plurality of heat sources comprises an aromaticscomplex-benzene extraction unit heat source comprising a heat exchangerthat is fluidly coupled to an overhead stream, and is fluidly coupled tothe first heating fluid circuit; and a fourth sub-set of the firstplurality of heat sources comprises at least four continuous catalyticcracking heat sources, comprising: a first continuous catalytic crackingheat source comprising a heat exchanger that is fluidly coupled to a CCRlast stage reactor outlet after a feed-effluent heat exchanger stream,and is fluidly coupled to the first heating fluid circuit, a secondcontinuous catalytic cracking heat source comprising a heat exchangerthat is fluidly coupled to a 1st stage compressor outlet stream, and isfluidly coupled to the first heating fluid circuit, a third continuouscatalytic cracking heat source comprising a heat exchanger that isfluidly coupled to a 2nd stage compressor outlet stream, and is fluidlycoupled to the first heating fluid circuit, and a fourth continuouscatalytic cracking heat source comprising a heat exchanger that isfluidly coupled to a CCR light reformate splitter column overheadstream, and is fluidly coupled to the first heating fluid circuit. 19.The method of claim 18, wherein a first sub-set of the second pluralityof heat sources comprises at least three para-xylene separation unitheat sources, comprising: a first para-xylene separation unit heatsource comprising a heat exchanger that is fluidly coupled to an extractcolumn overhead stream, and is fluidly coupled to the second heatingfluid circuit, a second para-xylene separation unit heat sourcecomprising a heat exchanger that is fluidly coupled to a Raffinatecolumn overhead stream, and is fluidly coupled to the second heatingfluid circuit, and a third para-xylene separation unit heat sourcecomprising a heat exchanger that is fluidly coupled to a heavy Raffinatesplitter column overhead stream, and is fluidly coupled to the secondheating fluid circuit.
 20. The method of claim 19, wherein a firstsub-set of the third plurality of heat sources comprises at least threediesel hydrotreating reaction and stripping heat sources, comprising: afirst diesel hydrotreating reaction and stripping heat source comprisinga heat exchanger that is fluidly coupled to a light effluent to coldseparator stream, and is fluidly coupled to the third heating fluidcircuit, a second diesel hydrotreating reaction and stripping heatsource comprising a heat exchanger that is fluidly coupled to a dieselstripper overhead stream, and is fluidly coupled to the third heatingfluid circuit, a third diesel hydrotreating reaction and stripping heatsource comprising a heat exchanger that is fluidly coupled to a dieselstripper product stream, and is fluidly coupled to the third heatingfluid circuit; and a second sub-set of the third plurality of heatsources comprises at least seven hydrocracking plant heat sources,comprising: a first hydrocracking plant heat source comprising a heatexchanger that is fluidly coupled to a 2nd reaction section 2nd stagecold high pressure separator feed stream, and is fluidly coupled to thethird heating fluid circuit, a second hydrocracking plant heat sourcecomprising a heat exchanger that is fluidly coupled to a 1st reactionsection 1st stage cold high pressure separator feed stream, and isfluidly coupled to the third heating fluid circuit, a thirdhydrocracking plant heat source comprising a heat exchanger that isfluidly coupled to a product stripper overhead stream, and is fluidlycoupled to the third heating fluid circuit, a fourth hydrocracking plantheat source comprising a heat exchanger that is fluidly coupled to amain fractionator overhead stream, and is fluidly coupled to the thirdheating fluid circuit, a fifth hydrocracking plant heat sourcecomprising a heat exchanger that is fluidly coupled to a keroseneproduct stream, and is fluidly coupled to the third heating fluidcircuit, a sixth hydrocracking plant heat source comprising a heatexchanger that is fluidly coupled to a kerosene pumparound stream, andis fluidly coupled to the third heating fluid circuit, and a seventhhydrocracking plant heat source comprises a heat exchanger that isfluidly coupled to a diesel product stream, and is fluidly coupled tothe third heating fluid circuit.
 21. A method of recovering heat energygenerated by a petrochemical refining system, the method comprising:identifying, in a geographic layout, a first heating fluid circuitthermally coupled to a first plurality of heat sources from a firstplurality of sub-units of a petrochemical refining system, the firstplurality of sub-units comprising a continuous catalytic reforming (CCR)and aromatics refining system; identifying, in the geographic layout, asecond heating fluid circuit thermally coupled to a second plurality ofheat sources from a second plurality of sub-units of the petrochemicalrefining system, the second plurality of sub-units comprising the CCRand aromatics refining system; identifying, in the geographic layout, athird heating fluid circuit thermally coupled to a third plurality ofheat sources of a third plurality of sub-units of the petrochemicalrefining system, the third plurality of sub-units comprising ahydrocracking-diesel hydrotreating system; identifying, in a geographiclayout, a first power generation system that comprises: a first organicRankine cycle (ORC), the first ORC comprising (i) a first working fluidthat is thermally coupled to the first and second heating fluid circuitsto heat the first working fluid with the first and second heatingfluids, and (ii) a first expander configured to generate electricalpower from the heated first working fluid; and a control systemconfigured to actuate: a first set of control valves to selectivelythermally couple the first heating fluid circuit to at least a portionof the first plurality of heat sources, and a second set of controlvalves to selectively thermally couple the second heating fluid circuitto at least a portion of the second plurality of heat sources;identifying, in a geographic layout, a second power generation systemthat comprises: a second ORC, the second ORC comprising (i) a secondworking fluid that is thermally coupled to the second heating fluidcircuit to heat the second working fluid with the third heating fluid,and (ii) a second expander configured to generate electrical power fromthe heated second working fluid; and a control system configured toactuate a third set of control valves to selectively thermally couplethe second heating fluid circuit to at least a portion of the thirdplurality of heat sources; and identifying, in the geographic layout, apower generation system location to position the power generationsystem, wherein a heat energy recovery efficiency at the powergeneration system location is greater than a heat energy recoveryefficiency at other locations in the geographic layout.
 22. The methodof claim 21, further comprising constructing the petrochemical refiningsystem according to the geographic layout by positioning the pluralityof sub-units at the plurality of sub-unit locations, positioning thepower generation system at the power generation system location,interconnecting the plurality of sub-units with each other such that theinterconnected plurality of sub-units are configured to refinepetrochemicals, and interconnecting the power generation system with thesub-units in the first subset such that the power generation system isconfigured to recover heat energy from the sub-units in the first subsetand to provide the recovered heat energy to the power generation system,the power generation system configured to generate power using therecovered heat energy.
 23. The method of claim 21, further comprising:operating the petrochemical refining system to refine petrochemicals;and operating the power generation system to: recover heat energy fromthe sub-units in the first subset through the first heating fluidcircuit and the second heating fluid circuit; provide the recovered heatenergy to the power generation system; and generate power using therecovered heat energy.
 24. The method of claim 21, further comprisingoperating the power generation system to generate about 45 MW of power.